What's hot:

Today (Dec. 2), Britney Spears turns 31 years old and celebrates another successful year in the spotlight. It seems like just yesterday that the Louisiana native was introducing herself on "Total Request Live," but seven albums, millions of downloads and hundreds of huge shows later, Spears is now a veteran pop performer with an awe-inspiring list of accomplishments under her belt.

From her Justin Timberlake romance to her snake-wielding performance to her new beginning as an "X Factor" judge, take a look back at Spears' pop reign so far with these 10 defining moments in her 14-year career.

"...Baby One More Time" Hits Us All

Remember the first time you heard those three notes and then "Oh, baby, baby?" How about your first encounter with Britney in a schoolgirl's outfit, coolly dancing down that hallway in the music video? "...Baby One More Time," the title track from Spears' 1999 debut of the same name, arguably remains the pop star's most iconic song to date, hitting No. 1 on the Hot 100 and turning into one of the most successful debut singles of all time. Oh baby, baby, how were we supposed to know that a pop princess had just been born before our very eyes?

OOPS! Britney Does It Again

After bursting onto the scene in 1999 with "...Baby One More Time," Spears returned in full force one year later with the sophomore effort "Oops!... I Did It Again," one of the most successful female pop albums of all time. With over 1.3 million units sold in its first week of release, "Oops!" still holds the record for the highest sales in one week by a female artist ever. And along with the monster sales came a durable collection of hits, including "Lucky," "Stronger," and of course the title track, which Spears unforgettably performed in a skin-colored spandex get-up at the 2000 MTV Video Music Awards.

Britney + Justin = Pop Royalty

Before there was Justin and Selena, there was Justin and Britney: Spears and her fellow "Mickey Mouse Club" alum Justin Timberlake enjoyed a celebrity romance at the beginning of their budding careers, with the *N Sync star and the pop princess spending their 20th birthdays as pop culture's prettiest couple. Sadly, the good times would not last: Spears and Timberlake ended their relationship in 2002, and breakup anthems like JT's "Cry Me a River" resulted.

Britney Raises Eyebrows With "Slave" Performance

One year after Spears showed off some skin while performing "Oops!... I Did It Again" at the 2000 VMAs, the pop star once again courted controversy during her follow-up at the 2001 MTV ceremony. Performing the "Britney" lead single "I'm A Slave 4 U," Spears slithered onstage with a collection of live animals, and eventually danced while carrying a large albino snake draped across her shoulders. A little over two years after presenting her innocent image on the "...Baby One More Time" album cover, Spears had abruptly become an adult on the VMAs stage.

Britney Locks Lips With Madonna

Thought the python performance of "I'm A Slave 4 U" was Spears' most memorable VMAs moment? Think again. Just two years later, Madonna invited Spears, Christina Aguilera and Missy Elliott onstage for a performance of her single "Hollywood" to open the 2003 ceremony. Madge locked lips with Aguilera too, but it was the shared kiss with Spears, front and center on the VMAs stage, that the world will always remember. The stunt preceded the release of Spears' fourth album, "In The Zone," which featured Madonna on the single "Me Against The Music."

Britney Issues Classic Video for "Toxic"

While some may consider the music videos for "...Baby One More Time," "Piece of Me," "Overprotected" and "Stronger" to be all-around winners, it's hard to find a stronger clip of Spears' pop dominance than the 2004 video for "Toxic," which was Spears' most expensive video to date with a budget of $1 million. The espionage romp was voted by Billboard.com readers as Spears' best music video ever last year, and with good reason: nothing before or since has quite captured her sexy, vibrant spirit.

Blackout Hints At Eventual Comeback

The 2007 release of fifth studio album "Blackout" came at a highly troubled time for Spears: from her rocky romance with Kevin Federline to her struggles as a new mother to the shaved head to the rehab stint, Spears' personal life was in dire straits as she set out on promoting her new album. Still, "Blackout" was a forward-thinking batch of slinky electro-pop jams, and critics hailed the efforts while expressing concern for its creator's well-being. In hindsight, "Blackout" was the precursor to Spears' full-fledged comeback, which was fully realized when her personal issues stabilized.

Britney Seizes Control on "Circus" Tour

If "Circus," Spears' sixth studio album, was the full-length that proved that the pop star was not going anywhere despite her dramatic past, the accompanying Circus tour was her victory lap, and the epic live show that she was born to put on. Combining six albums worth of hits with an ambitious stage setup featuring acrobats, martial artistry and a dazzling light show, Spears' Circus trek ran for eight months and entertained nearly 100 venues across the globe. Out of her seven full tours, Spears' Circus is still her defining run of shows.

Britney Makes Award Show Comeback at BBMAS

After a run of shocking MTV Video Music Awards performances early in her career, Spears, mired in her darkest personal period, was heavily panned when presenting "Gimme More" at the 2007 ceremony. But less than four short years later, Spears triumphantly returned to the spotlight at the 2011 Billboard Music Awards, where she made a surprise appearance during both Rihanna's opening number "S&M" as well as Nicki Minaj's set. Months after releasing another well-received album, "Femme Fatale," Spears had washed away the "Gimme More" memories in one fell swoop.

Britney Finds Her "X Factor" on TV

In the second season of the U.S. version of "The X Factor," Simon Cowell and Antonio "L.A." Reid welcomed Demi Lovato and none other than Ms. Spears herself to the judges table. Spears' first stint as a reality competition figure has been entertaining thus far, as Spears gets to flaunt her personality while adding a new dimension to her long-running career. Over a decade after bursting onto the scene as a teenager, Spears now gets to help guide aspiring vocalists, and help them find their own "Oh baby, baby" moment.